1. Technical Field
The present invention relates to a lubricating oil composition.
2. Description of the Related Art
A lubricating oil is used to reduce the frictional force that occurs on the frictional surface of machines or to disperse frictional heat generated on the frictional surface, and is utilized in various areas including precision machines, spindles, dynamo, steam turbines, compressors, motors, aircrafts, cylinders, etc.
Generally, a lubricating oil results from mixing 80˜90% of a base oil comprising mineral oils (paraffinic, naphthenic, aromatic oil) produced from a process of refining petroleum products or synthetic oils (alkylbenzene, PAO, PAGs, PB, ester, VHVI) with 10˜20% of an additive for improving lubrication functionality. Although the properties of a lubricating oil slightly vary depending on its end use, it typically has {circle around (1)} a viscosity maintained to be suitable for the use temperature and simultaneously which should not drastically change even upon changing the use temperature, {circle around (2)} a stable oil film that is formed even under boundary lubrication conditions, and {circle around (3)} a high stability to heat and oxidation.
The lubricating oil is also utilized for the dynamic fluid bearing of a spindle motor for a hard disk. In the case of a hard disk, products having the large capacity of 1 TB or more are currently available, and hard disks are expected to be developed to have a capacity increased by 1.8 times after one year, 3.2 times after two years, and 10 times after five years. According to the trend to increase hard disk capacity and decrease their sizes, the spindle motor is required to have high-precision rotation and great impact resistance, and thus the lubricating oil of the dynamic fluid bearing is regarded as important because it affects these operations so that the motor satisfies the above requirements.
In particular, in the case of a motor for use in a hard disk having a size of 2.5 inches or less, the lubricating oil is required to have low viscosity so that low power is consumed, and also must be stable at high temperature.